removal of c/u front to inspect before testing

[zeff737]

hi there, our tutor is a bit of a pratt! he is confusing us asto weather it is safe

to remove the fuse box cover to do our inital inspection before testing. He keeps saying "is there ANY chance of electric shock when removing the cover?" as i have not inspected that all the conductors are safely connected etc i have to answer yes, there is a chance...so he says that i can not continue as it would not be safe to do so....but unless i take off the cover and inspect the conections (with the main isolator off) how can i confirm that it is safe ...to remove the cover if you see what i mean? :|

could you tell me the correct order i need to do assuming that this is a brand new instalation, im guessing that that means when i come to it the main isolator will be in the off position. does this mean i can lock it off, then take off the cover then test the out going tails from the main isolator to confirm that the unit is dead, then start to inspect it?

 

[NozSpark]

Theoretically you are stuck in a catch 22..

But what you should do is isolate, remove cover, prove safe isolation and then carry out your work/inspection

IMO you only need to lock off if you are working remotely from the point of isolation.

 

[SPECIAL LOCATION]

Hello Zeff, there are various answers to this in the real world:-

1/ If you are talking about Initial inspection on a new installation, one would assume it hasn't been energised yet because it has not been fully inspected, tested & certified to ensure it is safe to energise!

2/ If as you say there may be incoming live tails to a switch in the off possition..... then you have got to get the cover off to test if they are live!!!? Personally I wouldn't lock off a main switch until I have verified it is working..

e.g. check power there, turn off check dead, check tester still OK. I would also double check BOTH poles of the switch are working, i.e. with the switch off test between Incoming 'L' & outgoing 'N' and vice-versa. and check both outgoing L & N to E. ( I have had a switch only isolating 1 pole before now! not good if only switching N off!! )

3/ Existing installation, 'Domestic' verify with the customer if the installation can be turned off? If yes then kill the power & remove cover.

4/ Existing installation, 'Non domestic' most often it is NOT practical to remove power to the whole installation, e.g. some essential services must retain power. So you have to remove front cover with care!

5/ Modern fully insulated CU generally have secondary barriers over the bus bar so risks reduced.

6/ Older "wylex" wire fuse jobbies typically have exposed bus bar... BUT a lot of the time you have to remove all of the fuse carriers to get the cover off.. so if all the fuse carriers have to come out.. you may as well kill the main switch!!

7/ I think the bottom line is it would be preferable where feasible to isolate the mane switch before remove the front cover.. But on occasions it is not practical, so treat such occasion with care and take due diligent to any other factors which could influence such a risk assessment..

e.g. is the CU in a location exposed to other members of the public, dont leave it unattended with a cover removed.. Beware of inquisitive children poking things in an open CU! etc.. etc...

HTH :coffee

 

[ADS]

I agree fully with Special Location - nothing else to add

 

[Doc Hudson]

hi there, our tutor is a bit of a pratt! he is confusing us asto weather it is safe to remove the fuse box cover to do our inital inspection before testing. He keeps saying "is there ANY chance of electric shock when removing the cover?"......

May be your tutor is playing devils advocate? just trying to get you to full think through the options, consequences and risks?. I think as the others have pointed out electrical work is not always a clear cut do A and B to get to C.

Doc H.

 

[0151]

there is actually a case going on now were the HSE are prosecuting an electrical contractors for taking the cover off a live board. depending on the outcome it may set a presedent for all sparks who test to have a live working authourisation certification and equipment (rubber under gloves, leather gauntlets, visor, insulated rubber mating, insulated tools and a qualified safety mate) try pressing the "test" button with all that on never mind the added costs

 

[M107]

Specs has said it all but I also put the old socket tester in to a local socket get the tone, then dump main switch on cu , tone stops I know the main switch is working & installation is isolated. I then do the normal safe isolation procedure once the cu cover is off.

 

[Andy™]

Specs has said it all but I also put the old socket tester in to a local socket get the tone, then dump main switch on cu , tone stops I know the main switch is working & installation is isolated. I then do the normal safe isolation procedure once the cu cover is off.

but what if it only isolates neutral? does it still sound with L-E voltage?

 

[NozSpark]

Mine does..

 

[Lurch]

Mine does..

As does mine.

 

[M107]

Sorry got side tracked ......... it does & the tone changes.......so I'm told.

 

[Lurch]

Sorry got side tracked ......... it does & the tone changes.......so I'm told.

Mine goes from a constant tone for correct connection to a warble tone for anything incorrect, other than no phase and then obviously it won;t do anything.

 

[zeff737]

so let me get this nailed down, when i aproach the test board (2330 level the inspection and live tests) for the first time and i HAVE to remove the cover to inspect it so all i need do is check the main isolator is off, remove the cover with due care, perform safe isolation, then start work?

A fellow student had done all the inspection and dead tests and had replaced the cover...upon removing it to start the live test (this time with the test rig energized) our tutor asked him "what gives you the right to remove that cover (or words to that effect)

my mate replied that he was "a compitent person" our tutor went nuts with him and said thats the wrong answer! (its the one our other tutor told us to say) the right answer was that he had inspected the system in a dead state and he was happy that he had limited the risks as far as possible......so there we are at the start again!!! headbang

 

[M107]

so let me get this nailed down, when i aproach the test board (2330 level the inspection and live tests) for the first time and i HAVE to remove the cover to inspect it so all i need do is check the main isolator is off, remove the cover with due care, perform safe isolation, then start work?

In a nut shell yes.

A fellow student had done all the inspection and dead tests and had replaced the cover...upon removing it to start the live test (this time with the test rig energized) our tutor asked him "what gives you the right to remove that cover (or words to that effect)

What test was he wanting to undertake with the cu energised & cover off?

 

[Andy™]

Mine does..

thats okay then (mine doesnt have sound, so no idea if it would make a noise or not). but either way, it would still be lit if there was a live

 

[zeff737]

In a nut shell yes.What test was he wanting to undertake with the cu energised & cover off?

I think it must have been polarity of the tails as we have been shown to test them across the terminals of the main isolator of the c/u.

 

[Buildall]

You would need the cover off to do a PFC test.

 

[Doc Hudson]

Even if switched off with the cover removed the incoming tails will still be live. So you will never isolate everything in the CU, unless the main fuse is disconnected of course?

Doc H.

 

[bulmer]

Suprised they haven't started putting shrouds over the incoming side of the main switch yet, what with all the HSE stuff nowadays.

 

[sellers]

from memory on some college test rigs there are seperate isolators before the board, you can do you isolation there and then take the cover off and nothing in the board will be live.

Then do your test for dead on the incomming tails. (don't forget proving leads before and after!!)